Apparatus for pouring molten metal from a ladle

ABSTRACT

High quality centrifugally cast cylindrical members are obtained by varying the rate of rotation of the metal pouring ladle during casting to obtain a more rapid angular displacement of the ladle at the initiation and termination of the pour than at the middle of the pour. Because the weight of the molten metal tending to discharge the metal from the ladle varies inversely with angular displacement of the ladle, i.e., the weight of molten metal at the discharge lip is maximum at the middle of the pour cycle, a substantially constant volume of metal is discharged throughout the pour. In a preferred embodiment of this invention, the rate of displacement of the ladle during the pour is symmetrical with the rate of ladle displacement being reduced from a predetermined speed during the first half of the pour and gradually increased to approximately the initial ladle displacement rate over the second half of the pour.

APPARATUS FOR POURING MOLTEN METAL FROM A LADLE 1 June 25, 1974 PrimaryExaminer-J. Spencer Overho1ser Assistant ExaminerV. K. Rising Attorney, Agent, or FirmVale P. Myles [57] ABSTRACT High quality centrifugally cast cylindrical members are obtained by varying the rate of rotation of the metal pouring ladle during casting to obtain a more rapid angular, displacement of the ladle at the initiation and termination of the pour than at the middle of the pour. Because the weight of the molten metal tending to discharge the metal from the ladle varies inversely with angular displacement of the ladle, i.e., the weight of molten metal at the discharge lip is maximum at the middle of the pour cycle, a substantially constant volume of metal is discharged throughout the pour. In a preferred embodiment of this invention, the rate of 3 Claims, 5 Drawing Figures [75] Inventor: William Russell Smith, Ballston Lake, NY.

[73] Assignee: General Electric Company,

Schenectady, NY.

[22] Filed: Aug. 4, 1972 [21] Appl. No.: 278,154

[52] US. Cl 164/300, 164/301, 164/336 [51] Int. Cl B22d 13/10 [58] Field of Search 164/300, 301, 299, 298

[56] References Cited UNITED STATESPATENTS 1,286,555 12/1918 DeLavaud l64/30OX 1,309,823 7/1919 Stokes 164/300 1,737,459 11/1929 Hurst et a1. 164/300 1,917,872 7/1933 Campbell 164/300 X 1,963,149 6/1934 Russell et a1 164/300 X w a a o PATENTED JUNE 5 i974 SHEET 2 0F 4 PATENTEDJUHZSIQH SHEET 3 OF 4 PATENTEU JUN25 74 SHEET Q 0F 4 mdE nmdm Dmmmm nm uE zoEaFom 2.0mm

APPARATUS FOR POURING MOLTEN METAL FROM A LADLE This invention relates to a method and apparatus for pouring molten metal from a ladle during centrifugal casting. More specifically, the invention relates to a variable speed ladle rotation mechanism for producing a more rapid rotation of the ladle at the initiation and termination of the pour than at the middle of the pour to produce a constant volumetric flow of metal from the ladle.

In the centrifugal casting ,of cylindrical structures, a quantity of molten metal typically is deposited in a ladle and,'after insertion of the ladle into the rotating mold, and ladle is rotated to discharge the molten metal from the ladle into the mold for solidification. In order to obtain a high quality cast structure, it generally is desirable to rotate the ladle gradually to obtain a uniform pour from the initial discharge of molten metal from the ladle to the termination of the pour. Although the desirability of a uniform pour heretofore has been known, see for example US. Pat. No. 1,917,872, the method utilized for obtaining the uniform pour normally has been the admission of a fluid, such as air, at a constant rate to the rotary drive mechanism for the ladle to produce a constant rate of angular displacement of the ladle. Although casts of good quality heretofore have been achieved utilizing constant ladle displacement rates, I have discovered that superior quality in cast cylindrical objects can be obtained by decreasing the angular displacement of the ladle during the first half of the pouring cycle. Although the exact reason for this phenomenon is not known with certainty, it is postulated that the weight of molten material at the discharge spout of the ladle increases during the initial half of the pour to discharge a substantially constant volume of material from the ladle with time.

It is therefore an object of this invention to provide a ladle rotating mechanism for centrifugally casting structures of superior quality.

It is also an object of this invention to provide a ladle rotation mechanism capable of obtaining a substantially constant discharge rate of molten metal from a ladle.

It is a further object of this invention to provide a method of centrifugally casting cylindrical structures while maintaining the discharge of molten metal from the ladle substantially constant.

As was heretofore stated, these and other objects of this invention generally are achieved by varying the rate of the ladle rotation during a single pour to produce a more rapid angular displacement of the ladle at the initiation of the pour than at the middle of the pour. Thus, a ladle rotating mechanism in accordance with this invention would include a vessel, such as a cylindrical ladle, capable of retaining molten material therein for a predetermined period of time and means for pouring of the molten material from an orifice situated in the upper portion of the vessel. The ladle rotating mechanism also contains means for controlling the rotational rate of the ladle during a single pour to reduce the speed of the angular displacement of the ladle during the first half of the pour and gradually increase the rotational speed of the ladle during the second half of the pour to produce a substantially continuous volume of metal flow from the ladle during the complete pour cycle.

While this invention is described with particularity in the appended claims, a more complete understanding of the invention may be obtained from the following detailed description of a specific embodiment of the invention when takenin conjunction with the appended drawings wherein:

FIG. 1 is an elevational view of a rotatable ladle in accordance with this invention,

FIG. 2 is a view of the ladle rotation mechanismutilized to pour molten metal from the ladle,

FIG. 3 is a view of the control mechanism employed for obtaining a variable angular displacement rate in the ladle,

FIG. 4 is a graph illustrating the variation of the rate of angular displacement of the ladle with the pour cycle, and

FIG. 5 is a pictorial illustration depicting the deposition of molten metal within the ladle at various stages of the pour.

A ladle 10 having a controlled rate of angular displacement in accordance with this invention is illustrated in FIG. 1 and generally comprises a cylindrical vessel 12 secured to the end of shaft 14 proximate mold 16 to deposit molten material, e.g., liquid aluminum, into the rotating mold to cast a cylindrical structure, such as a finned motor frame. The vessel is carried upon a carriage 18 which is axially traversable along rails 20 to insert the vessel within the mold whereafter the vessel is rotated by rotational mechanism 22 secured to the end of shaft 14 remote from the ladle. A rotational mechanism for applying controlled torque to vessel 12 and a carriage for insertion of the ladle within the rotating mold is described in co-pending U.S. application, Ser. No. 277,920 entitled Horizontal Centrifugal Casting Machine filed in the name of F. W. Baumann et al and assigned to the assignee of the present invention, (the entire disclosure of which application is incorporated herein by reference).

Cylindrical vessel 12 preferably has an exterior metallic sheathing 24 and an inner ceramic lining 26 to maintain the molten metal within the vessel at elevated temperatures prior to casting. In conventional fashion, a rectangular opening 28 is provided in the upper surface of the cylindrical vessel to permit filling of the vessel and the subsequent controlled discharge of molten metal from the vessel. Typically, opening 28 extends at least percent of the length of the vessel to equalize the pour region over an elongated axial length of the mold and the longitudinal sides of the opening are spaced by a span, typically between 40 and permitting a rapid pour of molten metal from the vessel. It will be appreciated, however, that other geometric configurations also could be utilized for the ladle to be controllably rotated in accordance with the teachings of this invention. For example, rather than a rectangular opening in the vessel, the entire upper portion of vessel 12 could be removed. Alternatively, the ladle could be a rotatable cup like vessel mounted upon a rotatable shaft and having a side pour spout upon the upper lip of the vessel for the discharge of metal from the vessel.

Referring more particularly to FIG. 2, rotational mechanism 22 for the ladle basically includes a hydraulic cylinder 30 for driving a rod 32 meshed with a pinion 34 fixedly mounted upon shaft 14. The drive force for the rod is provided by hydraulic fluid admitted to cylinder 30 from source 36 through valve 38 disposed i in hose 401in'terconnecting' the cylinder with: the hy-- draulic fluid sourcetAs hy raulic fluidis admitted as; l cylinde'ri30,rod 32 is driven outwardly" fromi thecylinder to rotate cylindrical vessel 12 and metalfrom the vessel intotthe mold; V

J In accordance with this ,invention theqrate of admis sion of hydraulic fluid to cylinder 30-is varied during the pour to obtain a uniform rate of molten metaldischarge from, ladle 10. As can be seen in'FIG.'3, the vari- 'able rate of angular displacement 'of the ladle is ob,

pouremoltenf tained by a tapered cam 42 which engages control unit 44 of valve 38 to vary the orifice within the valve to produce a faster, rate of angular displacementof the] ladle at theinitiation'andtermination of the pour than at the middle of the pour (as is shown in the graph of FIG. 4). Thus, rather than using a continuous rate of. I

angular displacement of the ladle, the ladle is rotated at a'rapid, preferably uniform,xrate at the initiation'of 7 the pour of molten metal from rectangular opening 128," and the rate of ladle rotation-is gradually decreased FIG. approximately of the ladle atthe initiati'on of the discharge: I

I While a specific embodiment of this inventionhasbeen 'illustratedand described, i tlwill be: obvious toa those skilledin the art that many variations can" be 'made in'the structural 'vfeatu re's of: therotatingmecha nism without departing from the scope of this inven tion. For example, rather thanemploying a tapered cam fixedly secured to rod 32m regulate control unit 44., the cam could be a circular cam mounted upon shaft 14 to engage roller 48 of the control unitl'intend. therefore by the appended claims to cover all such 4 1 modifications and changes as fall within' 'the true spirit f;

predeterminedvolume ofmolten metal into a centrifu- 1 V 7 gal casting mold, the combination of a ladle (l0) rotatalong line A until approximatelyone-half of themolteni metal'withinithe ladle is discharged from the ladle; At"

such time, the upwardly tapered face 46 of cam 42 engages control unitz44 to gradually increase the. rate of hydraulic fluid flow to hydraulic cylinder 30 andflthe rate of rotation of the'ladle isincreased along line B to 'mannerpthe volume of metal per unit time discharged ably mounted upon a movable carriage (18), a centrii riage,'said carriage being operable to insert the; ladle 7 into. said mold in response to the: carriage beingrmovedt i toward the mold, a rotationalmechani'sm (22') coupled 9 I to the ladle for applying torque to rotate it at a controlled rate, thereby to affordia predetermined variable 7 rate ofrangular displacement of the ladle;a control unit from the ladle is substantially'constant throughoutthe T pour and'the quality ofthe cast structure is improved relative to cast structures formed by tilting the ladle at a uniform displacement rate. Furthermore,lbecause the rate of rotation of the ladle is'reduced at the middleof 7 the pour, the amount of splashingin the mold iszre-" duced. ln' general, themaximumrate of ladledisplace;

ment andr thechange in theirate of;ladlerotationwill vary dependent upon such factorsas the size of the cylinder is gradually reduced, preferably in'an approxi mately linear fashion, until about one-half of the molten metal within the vessel is discharged from the vessel (as shown in FIG. 5C); At such time, upwardly tapered face 46 engages the roller of the control unit and the flow of hydraulic fluid through the control unit is gradually increased to increase the rate of rotation of the ladle. Preferably, the control unit is positioned relative tothe cam so that the final rotational speed of the ladle upon discharge of molten metal therefrom (as shown in (44) operativelycoupled 'to the rotational mechanism to control the rate of rotation thereof, a tapered cam (42) mounted: on said rotational mechanism for'relative movement withrespect "to said control unit, said I a cam being in'engagement with acam. follower (48-) that is operably coupledto the control unit (44 ),to cause it to vary the rate of angular displacement of the ladle in response to: the cam .followerb'eing, moved relative to the control unit, said tapered cambeing. operable in combination with the cam follower, control unit and rectangular opening of the ladle, the height ofth'e m olten, metal in the ladle, the interior configurationofthe fmold; etc'sand can bestbe determined empiricallyrfor' 7 each frame size to be'cast byaparticular ladle. f

7 At the initiation of'a' pour cycle, vessel I2is fillcdias shown in FIG. 5A)and roller 48 0fcontrolunit 44 is 'f;

' engaged by cam '42 at surface 50 (perpendicular to the rotational mechanism to produce a rapidangular dis I placement of the: ladle at the initiation: ofa pour cycle followed by a generally, linear reduction. in the rate of i rotation of the ladle unit approirimatelyone-half of the.

predetermiend volume of metal in the ladle is discharged, followed by a-generailylinearincrease inthej ,t 7 rate ofrotation of the ladle during thcglatterhalf of the: t I pour cycle until the rate ofrotationapproximatesthat V achieved at the initiation of the pour cycle,

2. A ladle rotating mechanism according to claim-l wherein said ladle is a cylindrical vessel (12") having an axis of rotation disposed in a substantially horizontal plane and having an orifice (28) comprising a generally rectangular opening. therein, and wherein said control unit for varying the rate of rotation includes a cam actuated valve that is connected to a pressurized source" said V-shape.

edual to the rotationalspeed V Y 

1. In a ladle rotating mechanism for use in pouring a predetermined volume of molten metal into a centrifugal casting mold, the combination of a ladle (10) rotatably mounted upon a movable carriage (18), a centrifugal mold (16) operably mounted proximate said carriage, said carriage being operable to insert the ladle into said mold in response to the carriage being moved toward the mold, a rotational mechanism (22) coupled to the ladle for applying torque to rotate it at a controlled rate, thereby to afford a predetermined variable rate of angular displacement of the ladle, a control unit (44) operatively coupled to the rotational mechanism to control the rate of rotation thereof, a tapered cam (42) mounted on said rotational mechanism for relative movement with respect to said control unit, said cam being in engagement with a cam follower (48) that is operably coupled to the control unit (44) to cause it to vary the rate of angular displacement of the ladle in response to the cam follower being moved relative to the control unit, said tapered cam being operable in combination with the cam follower, control unit and rotational mechanism to produce a rapid angular displacement of the ladle at the initiation of a pour cycle followed by a generally linear reduction in the rate of rotation of the ladle unit approximately one-half of the predetermiend volume of metal in the ladle is discharged, followed by a generally linear increase in the rate of rotation of the ladle during the latter half of the pour cycle until the rate of rotation approximates that achieved at the initiation of the pour cycle.
 2. A ladle rotating mechanism according to claim 1 wherein said ladle is a cylindrical vessel (12) having an axis of rotation disposed in a substantially horizontal plane and having an orifice (28) comprising a generally rectangular opening therein, and wherein said control unit for varying the rate of rotation includes a cam actuated valve that is connected to a pressurized source of fluid to vary the rate of flow of the fluid for applying torque to said ladle.
 3. An invention as defined in claim 1 wherein said tapered cam has a pair of linearly tapered surfaces (46, 54) that define a V-shape for controlling the movement of the cam follower, said V-shaped surfaces being disposed between a pair of linear surfaces that extend beyond the outer ends of the tapered surfaces in a plane that is substantially perpendicular to the vertical axis of said V-shape. 